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e468e2359a
Some games open two USB interfaces, e.g. /dev/usb/oh0 and /dev/usb/hid. This was causing us to run two scanning threads at once, using up more CPU time for scanning than we need to.
69 lines
1.7 KiB
C++
69 lines
1.7 KiB
C++
// Copyright 2025 Dolphin Emulator Project
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// SPDX-License-Identifier: GPL-2.0-or-later
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// Wrapper around Flag that lets callers wait for the flag to change.
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#pragma once
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#include <chrono>
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#include <condition_variable>
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#include <mutex>
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#include "Common/Flag.h"
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namespace Common
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{
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class WaitableFlag final
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{
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public:
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void Set(bool value = true)
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{
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if (m_flag.TestAndSet(value))
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{
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// Lock and immediately unlock m_mutex.
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{
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// Holding the lock at any time between the change of our flag and notify call
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// is sufficient to prevent a race where both of these actions
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// happen between the other thread's predicate test and wait call
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// which would cause wait to block until the next spurious wakeup or timeout.
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// Unlocking before notification is a micro-optimization to prevent
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// the notified thread from immediately blocking on the mutex.
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std::lock_guard<std::mutex> lk(m_mutex);
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}
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m_condvar.notify_all();
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}
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}
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void Reset() { Set(false); }
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void Wait(bool expected_value)
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{
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if (m_flag.IsSet() == expected_value)
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return;
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std::unique_lock<std::mutex> lk(m_mutex);
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m_condvar.wait(lk, [&] { return m_flag.IsSet() == expected_value; });
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}
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template <class Rep, class Period>
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bool WaitFor(bool expected_value, const std::chrono::duration<Rep, Period>& rel_time)
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{
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if (m_flag.IsSet() == expected_value)
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return true;
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std::unique_lock<std::mutex> lk(m_mutex);
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bool signaled =
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m_condvar.wait_for(lk, rel_time, [&] { return m_flag.IsSet() == expected_value; });
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return signaled;
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}
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private:
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Flag m_flag;
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std::condition_variable m_condvar;
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std::mutex m_mutex;
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};
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} // namespace Common
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